1. Field of the Invention
The present invention pertains to slide fasteners and more particularly to slide fasteners having fastener elements formed from a continuous filament of deformable material and a method for forming a top portion for such slide fasteners.
2. Description of the Prior Art
It is customary to provide end stops for slide fasteners; that is, a bottom stop for limiting opening movement of a slider and a top stop for limiting closing movement of the slider. The bottom stop for many applications is not externally visible after installation in a garment and is normally installed in a garment where the material is joined such that the bottom stop may have a variety of shapes without irritating the wearer of the garment, without adversely affecting its functional requirements and without hampering installation in a garment. Top stops, however, are relatively prominent and visible after installation in garments and must be precisely positioned with respect to the slide fastener to permit separation thereof.
In the past, a particular problem has been encountered in the top portion adjacent the top stop in that when the slider is positioned to engage the top stop the diamond of the slider is disposed between terminal fastener elements such that the upper ends of the slide fastener tape extending above the top stop are splayed. This splay is highly undesirable from an aesthetic standpoint and causes difficulties in installation of the slide fastener in a garment. These difficulties are accentuated as progress is made in the development of new techniques for quickly and automatically securing slide fasteners to materials, such as, the electrostatic methods now being incorporated into mass production lines.
Top stops for slide fasteners are conventionally made of bands of metal or other material, which bands are folded upon themselves and around cords on either side of the slide fastener tapes to which the fastener elements are attached. Such top stops have the disadvantages of being relatively difficult and expensive to form on the slide fasteners, and furthermore are unattractive as viewed from the exterior side of the slide fastener and are irritating to the wearer of the garment on the interior side of the slide fastener.
With the advent of slide fasteners utilizing fastener elements of filamentary plastic material, attempts have been made to provide top stops of similar plastic materials to reduce assembly and material costs as well as to permit dying of the top stops for aesthetic purposes. Such attempts have not met with success in that they have normally required the positioning of a bar of plastic material across the terminal fastener elements, which bar of material is fused with the tape and the fastener elements and then cut to provide two separate stop members. Prior art methods and apparatus for fusing such material along with the severing step have caused the final product to have considerable flash and jagged edges which require polishing or manual finishing prior to installation in a garment.
In order to permit installation of slide fasteners in a garment, it is normally required that the tape area above the top stop be flexible to permit folding of the tape during installation. It is accordingly, extremely desirable to have the upper edge of the top stop well defined; however, prior art top stops made of plastic material have not provided such definition.